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Physiology I > Lecture 3 Membrane Potentials and Action Potentials > Flashcards

Lecture 3 Membrane Potentials and Action Potentials Flashcards

1
Q

Cell Body

A

Houses the nucleus and other typical cell organelles
The plasma membrane around the cell body is characterized by local potentials
Voltage gated ion channels are NOT characteristic of the cell body membrane

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2
Q

Dendrites

A

Cellular extensions of the neuron
The number is typically a few to many
Dendrites are characterized by the presence of ligand (neurotransmitter) -gated channels
Conduct local potentials

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3
Q

This houses the nucleus and other typical cell organelles

A

The cell body

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4
Q

Dendrites conduct

A

Local potentials

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5
Q

Axon

A

A neuron characterized by a single axon that is variable in length
An extension of the cell body and is typically opposite the side of the cell body where the dendrites are located
An extension of the cell and is covered by the plasma membrane (axolemma)

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6
Q

Axolemma

A

Characterized by the presence of voltage-gated ion channels and the ability to conduct an action potential

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7
Q

Distal end of axon

A

Characterized by the presence of membrane-bound vesicles filled with neurotransmitters

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8
Q

Neuron is characterized by

A

a single axon this is variable in length

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9
Q

Myelinated axon looks like

A

sausage because it is myelinated

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10
Q

Telodendria

A

Means end branches

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11
Q

Cell membrane aka

A

Plasmalemma

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12
Q

Cell membrane functions to

A

maintain separate intracellular and extracellular environments

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13
Q

Ion concentrations between intracellular and extracellular environments

A

Can change depending on whether or not the plasmalemma is permeable to specific ions at given periods of time

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14
Q

These ions are more highly concentrated outside the cell

A

Sodium and chloride

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15
Q

Ion more concentrated inside of cell

A

Potassium

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16
Q

Diffusion Potential

A

A diffusion potential is caused by an ion concentration difference on the two sides of a membrane.
*transitory

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17
Q

Nernst Potential

A

The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane

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18
Q

Nernst Equation

A

E = +- 61 x log [Co]/[Ci]

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19
Q

Nernst Equation is used to determine

A

The diffusion potential across a membrane that exactly opposes the net diffusion of a particular ion through the membrane. It measures the potential for one ion at a time

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20
Q

Nernst Equation measures

A

The potential for one ion at a time

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21
Q

To measure the combined potential for more than one ion

A

The Goldman equation may be used

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22
Q

E =

A

The difference in the electrical potential between inside and outside the neuron
Nernst potential

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23
Q

Principal of electrical neutrality

A

At equilibrium the concentration of ions should be the same

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24
Q

Resting membrane potential of nerves

A

Sodium-Potassium pump

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25
Q

Characteristics of action potential

A

All or none, will occur or won’t
Self-propagating, each region of depolarization serves to generate action potentials on either side
Non-decremental, does not decrease in strength

26
Q

Action potential is all or none

A

It will either occur or not

27
Q

Action potential is self-propagating

A

each region of depolarization serves to generate action potentials on either side

28
Q

Action potential is non-decremental

A

It does not decrease in strength

29
Q

Ion channels

A

Are channels that allow the passage of ions from one side of the membrane to the other
Typically very selective, allowing only one kind of ion to pass through

30
Q

How selective are ion channels?

A

Very selective, one kind of ion is allowed to pass through

31
Q

Ion channels are open

A

When certain conditions are met

32
Q

Slow-leak channels are

A

always open

33
Q

Two types of gated ion channels are

A

Ligand gated

Voltage gated

34
Q

Voltage gated sodium channels have two gates

A

Activation Gate

Inactivation Gate

35
Q

Activation gate is closed at

A

-90mV

The resting potential

36
Q

-90mV

A

The activation gate is closed and the inactivation gate is opened
With the inside of the axon membrane negative relative to the outside

37
Q

Activation gate open, inactivation gate closed

A

+35mV - -90mV

38
Q

Potassium-gated channels

A

Have a single gate
Gate is closed at a resting potential of -90mV
Slow activation opens the gate from +35 mV to -90mV

39
Q

Action Potential Propagation

A

Steps in the generation of an action potential on a neuron axon membrane

  1. Resting Stage
  2. Depolarization Stage
  3. Repolarization Stage
  4. Sodium and potassium conductance
40
Q

Resting Stage

A

1st step in the generation of an action potential

-90mV

41
Q

Depolarization Stage

A

Membrane suddenly becomes permeable to sodium ions

Membrane potential may overshoot for large axons

42
Q

Repolarization Stage

A

Sodium channels close within a few 10,000ths of a second

Potassium channels open more than normal

43
Q

Action Potentials

A

Current flowing down the inside of an axon at a particular point can continue down the interior of the fiber or cross the membrane at that point.

44
Q

Threshold

A

Point at which a local potential will elicit an action potential
-65mV (highly variable)

45
Q

Action Potential Direction of Propagation

A

Action potential travels in all directions form the point of stimulation

  • Orthodromic direction
  • Antidromic direction
46
Q

Orthodromic Direction

A

Of an action potential

Direction normally taken

47
Q

Antidromic Direction

A

Of an action potential

Opposite direction than normally taken

48
Q

As K+ goes out…

A

Gets more negative because losing +

49
Q

Myelination - 3 parts

A
  1. Sphingomyelin
  2. Schwann cell
  3. Node of Ranvier
50
Q

Sphingomelin

A

(myelination)

Lipid, laid down by Schwann cells

51
Q

Schwann cell

A

(myelination)

Wraps around axons in peripheral nervous system

52
Q

Node of Ranvier

A

(myelination)

Gaps between Schwann cells, has to jump from one Node of Ranvier, called Saltory conduction

53
Q

Saltatory Conduction

A

Jumps from one node to the next

  1. Increases velocity of nerve transmission
  2. Allows 100x less loss of ions and requires little energy for repolarization
54
Q

Fiber diameter

A

If you increase diameter, can increase surface area, resistance decreases

55
Q

Characteristics of axon that carries signal the fastest

A

Myelinated axon
Large diameter
Ex. Skeletal muscle movement

56
Q

Characteristics of axon that carries signal the slowest

A

Nonmyelinated
Small diameter
Ex. Pain signals

57
Q

Function of a Schwann cell

A

to insulate nerve cells

58
Q

Where waves of depolarization occur

A

Node of Ranvier

59
Q

Absolute refractory period

A

Right after the action potential

Period during which a second action potential cannot be elicited even with a strong stimulus

60
Q

Relative refractory period

A

Stronger than normal stimulus can cause action potential

-usually in lab setting

61
Q

Changing ion concentrations

A

Describe how changes in environmental ion concentrations alter membrane potentials

Physiology I (7 decks)

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